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  <title>Filter flags</title>

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  <h2 class="title">Filter flags</h2>
  
  <p class="para">
   <table class="doctable table">
    <caption><strong>List of filter flags</strong></caption>
    
     <thead>
      <tr>
       <th>ID</th>
       <th>Used with</th>
       <th>Description</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td><strong><code>FILTER_FLAG_STRIP_LOW</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_ENCODED</code></strong>,
        <strong><code>FILTER_SANITIZE_SPECIAL_CHARS</code></strong>,
        <strong><code>FILTER_SANITIZE_STRING</code></strong>,
        <strong><code>FILTER_UNSAFE_RAW</code></strong>
       </td>
       <td>
        Strips characters that has a numerical value &lt;32.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_STRIP_HIGH</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_ENCODED</code></strong>,
        <strong><code>FILTER_SANITIZE_SPECIAL_CHARS</code></strong>,
        <strong><code>FILTER_SANITIZE_STRING</code></strong>,
        <strong><code>FILTER_UNSAFE_RAW</code></strong>
       </td>
       <td>
        Strips characters that has a numerical value &gt;127.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ALLOW_FRACTION</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_NUMBER_FLOAT</code></strong>
       </td>
       <td>
        Allows a period (<em>.</em>) as a fractional separator in
        numbers.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ALLOW_THOUSAND</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_NUMBER_FLOAT</code></strong>,
        <strong><code>FILTER_VALIDATE_FLOAT</code></strong>
       </td>
       <td>
        Allows a comma (<em>,</em>) as a thousands separator in
        numbers.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ALLOW_SCIENTIFIC</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_NUMBER_FLOAT</code></strong>
       </td>
       <td>
        Allows an <em>e</em> or <em>E</em> for scientific
        notation in numbers.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_NO_ENCODE_QUOTES</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_STRING</code></strong>
       </td>
       <td>
        If this flag is present, single (<em>&#039;</em>) and double
        (<em>&quot;</em>) quotes will not be encoded.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ENCODE_LOW</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_ENCODED</code></strong>,
        <strong><code>FILTER_SANITIZE_STRING</code></strong>,
        <strong><code>FILTER_SANITIZE_RAW</code></strong>
       </td>
       <td>
        Encodes all characters with a numerical value &lt;32.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ENCODE_HIGH</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_ENCODED</code></strong>,
        <strong><code>FILTER_SANITIZE_SPECIAL_CHARS</code></strong>,
        <strong><code>FILTER_SANITIZE_STRING</code></strong>,
        <strong><code>FILTER_SANITIZE_RAW</code></strong>
       </td>
       <td>
        Encodes all characters with a numerical value &gt;127.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ENCODE_AMP</code></strong></td>
       <td>
        <strong><code>FILTER_SANITIZE_STRING</code></strong>,
        <strong><code>FILTER_SANITIZE_RAW</code></strong>
       </td>
       <td>
        Encodes ampersands (<em>&amp;</em>).
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_NULL_ON_FAILURE</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_BOOLEAN</code></strong>
       </td>
       <td>
        Returns <strong><code>NULL</code></strong> for unrecognized boolean values.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ALLOW_OCTAL</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_INT</code></strong>
       </td>
       <td>
        Regards inputs starting with a zero (<em>0</em>) as octal
        numbers. This only allows the succeeding digits to be
        <em>0-7</em>.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_ALLOW_HEX</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_INT</code></strong>
       </td>
       <td>
        Regards inputs starting with <em>0x</em> or
        <em>0X</em> as hexadecimal numbers. This only allows
        succeeding characters to be <em>a-fA-F0-9</em>.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_IPV4</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_IP</code></strong>
       </td>
       <td>
        Allows the IP address to be in IPv4 format.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_IPV6</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_IP</code></strong>
       </td>
       <td>
        Allows the IP address to be in IPv6 format.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_NO_PRIV_RANGE</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_IP</code></strong>
       </td>
       <td>
        <p class="para">
         Fails validation for the following private IPv4 ranges:
         <em>10.0.0.0/8</em>, <em>172.16.0.0/12</em> and
         <em>192.168.0.0/16</em>.
        </p>
        <p class="para">
         Fails validation for the IPv6 addresses starting with
         <em>FD</em> or <em>FC</em>.
        </p>
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_NO_RES_RANGE</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_IP</code></strong>
       </td>
       <td>
        Fails validation for the following reserved IPv4 ranges:
        <em>0.0.0.0/8</em>, <em>169.254.0.0/16</em>,
        <em>192.0.2.0/24</em> and <em>224.0.0.0/4</em>.
        This flag does not apply to IPv6 addresses.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_PATH_REQUIRED</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_URL</code></strong>
       </td>
       <td>
        Requires the <acronym title="Uniform Resource Locator">URL</acronym> to contain a path part.
       </td>
      </tr>

      <tr>
       <td><strong><code>FILTER_FLAG_QUERY_REQUIRED</code></strong></td>
       <td>
        <strong><code>FILTER_VALIDATE_URL</code></strong>
       </td>
       <td>
        Requires the <acronym title="Uniform Resource Locator">URL</acronym> to contain a query string.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
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